Ask a Question forum: Neem Oil Question

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Eastern Tennessee (Zone 7a)
Jul 24, 2017 8:31 PM CST
Earlier in the year I took a morning stroll through the tomato plants and noticed that one of them had a huge infestation of aphids. I then proceeded to go back through and check other plants to see how far the little buggers had got. Luckily I caught them early and only a couple other plants had them and they were very few in number. So i head out and grab the sprayer and mix up a batch of neem oil and dish soap, sprayed pretty heavily hoping I got them early and they wouldnt have a chance to get really bad. Four days later I return and start a good check - not an aphid in sight - even in the really badly infested plant - poof - no aphids. I thought hey great I got them early im golden but as I was checking them I noticed that many of the plants now had blight.
Before I go any further some variables - We had a very wet spring, I used ground cover on the tomatoes, no tomatoes had been planted anywhere near there in 8 years or more if ever, that was the first spraying of any kind, no watering had been done or needed.

Now I am well aware of how blight is supposed to spread so is it possible that by using an oil based product, that I have effectively made the foilage sticky and actually helped the spores setup on the plant? Has anyone ever heard of this or has there been some kind of research done on this?

Clearly there is no way I can prove that this is what happened but I am wondering If maybe I made the tomatoes more susceptible to blight by making their leaves sticky with the neem oil and dish soap?
[Last edited by Nominix - Jul 24, 2017 9:06 PM (+)]
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Name: Daisy I
Reno, Nv (Zone 6b)
Not all who wander are lost
Garden Sages Plant Identifier
Jul 24, 2017 9:49 PM CST
Photos would be good.

Did you spray the Neem onto your plants in the morning when you saw the aphids? If so, your plants could be suffering some burn. Neem is really hard on plants in the sun and is always recommended to be sprayed in the evening after the sun has set.
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming...."WOW What a Ride!!" -Mark Frost

Eastern Tennessee (Zone 7a)
Jul 24, 2017 10:10 PM CST
I sprayed them that morning given that it was supposed to be overcast the entire day - which it was, and it was pretty early in the season and temps had not started to get above high 70's to maybe a day or 2 of 80. It was/is clearly blight. Bottom leaves turning yellow and brown and it has been working its way up all season. I have been keeping it somewhat delayed with copper spray but I am going to destroy 2 plants tomorrow and do a heavy prune on the rest to see if I can stave it off a bit longer. NC got hit very hard last year with blight so I guess this year its TN's turn. I live in Eastern TN and am 30 min from either NC or VA so everyone was kind of figuring it would get to us sooner rather than later.

It just hit me tonight as I was looking for some better solutions to it that maybe I had inadvertently made the tomatoes more susceptible to it by putting the neem on it. If the neem does add a bit of stickyness that allows blight spores to readily adhere to the foliage I think maybe I need to come up with some other (organic) way to address aphids. But before I go changing anything around Id like to know if that is even valid.

I am planning to put the tomatoes in a different spot next year and in a high tunnel so I can trellis them and use a shade cloth so perhaps that will help some.
[Last edited by Nominix - Jul 24, 2017 10:13 PM (+)]
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